Digital Rights Management (DRM) refers to technologies that manage access to and usage of digital content such as songs and movies. DRM associated with some piece of digital content often requires a device (e.g., a personal computer or a digital audio player) to obtain a license before being allowed to consume the digital content. Typically, this license not only allows the device to consume the digital content, but also specifies rights or restrictions by which the device may do so. The license may, for instance, allow the device to play the digital content but not copy the digital content to a second device.
In some instances, content providers wish to only allow one or more content-consuming devices to preview a portion of a digital work, such as a song or movie. These content providers traditionally accomplish this task using one of three main techniques. First, the content provider may send only the portion of the digital work down to the device. The content provider includes with this portion a license that allows the device to consume that portion of the digital work. Unfortunately, if a user of the device enjoys the previewed content and wishes to purchase the entire digital work, that user must reconnect to a network to receive the entire digital work and an associated license. Often times, however, users listen to content on a digital audio player (DAP) or the like that does not so connect to the network.
In addition, these licenses traditionally bind to a single device, such that if the device such as the DAP shares the content with a second device, the second device must acquire another license. Again, this second device may not be connected to a network, and hence may not be able to preview the content.
A second traditional technique to provide a preview experience includes sending down the entire digital work, but only encrypting a portion of the work to which the device may not access. The remaining portion, meanwhile, is left unencrypted so as to allow the device to preview this portion. Unfortunately, this leaves that portion of the work unencrypted and, hence, unprotected. Because a portion of the work is unprotected, the user of the device may alter or copy the content of that portion.
A third and final traditional technique allows a content provider to separately stream, to a content-consuming device, only a portion of a digital work in a same file as that of the entire digital work. This allows the device to consume that portion and only that portion. Unfortunately, this separate stream results in additional overhead and does not lend itself to streaming multiple portions of a digital work in an efficient manner.